title: Alignment of dispersions of plate-like colloidal particles of Ni(OH)2 induced by elongational flow.
abstract: Small-angle neutron scattering, SANS, has been used to study the alignment of a sterically stabilized colloidal dispersion of nickel hydroxide induced by elongational flow. Two different concentrations, 20 and 23 wt %, of well-defined hexagonal platelets have been studied. Significant anisotropy in the scattering patterns has been observed for the higher concentration dispersion that increases with increasing elongational strain rate. The effect of pipe flow (shear flow) on the orientational ordering at the inlets is also described. Near the outlets there is also a shear stress and this tends to increase the alignment. The orientational distribution of the particles under flow is described in terms of an order parameter calculated with respect to an individual director for each scattering pattern. The experimental measurements are supported by comparison with computer simulations which help to explain the effects of local velocity on the alignment induced by elongational flow. A slight decrease in the observed alignment was found after continuous flow for approximately 30 min and possible reasons are discussed.
authors.affiliation: Division of Materials Physics, Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden. Junaid.Qazi@fysik.uu.se
authors.forename: S Junaid S
authors.initials: SJ
authors.lastname: Qazi
authors.forename: Adrian R
authors.initials: AR
authors.lastname: Rennie
authors.forename: Ian
authors.initials: I
authors.lastname: Tucker
authors.forename: Jeff
authors.initials: J
authors.lastname: Penfold
authors.forename: Isabelle
authors.initials: I
authors.lastname: Grillo